Various power modules such as an inverter for driving an alternating-current motor, a power conditioner for solar power generation, and the like are electric components configured to perform a power conversion operation with integrated semiconductor elements.
Such a power module is provided by integrating not only semiconductor elements but also a case, a sealing gel, an electric interconnection, an insulating substrate, and a base plate. Further, a gate driver circuit and a protection circuit for preventing overheat and overcurrent are also integrated, depending on a kind of a power module. Therefore, convenience for a user who designs and manufactures a product using a power module is provided.
Since a sudden failure of a power module leads to stop equipment and a device to which the power module is applied, it causes economical loss and the like. Therefore, there has been a known attempt to diagnose a service life of a power module.
For example, according to the method disclosed in Japanese Patent Laying-Open No. 2011-196703 (PTD 1), an entire operational temperature range of a semiconductor device constituted of power semiconductor elements is divided into a plurality of temperature regions, and the number of cycles is calculated with use of values weighted to the number of power cycles in respectively set reference temperature differences within the temperature region. Further, according to this method, the service life is estimated by calculating an accumulated damage with use of the Miner's law based on each of the calculated number of cycles between the divided temperature regions.